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I have a UX31-E Asus Zenbook running 12.04 until today when I tried 12.10. I've experienced this issue on both versions of ubuntu.
I have tried turning the brightness down manually through the settings manager as well as trying to set it using my function keys. Either way works fine while I'm actively using the computer. After a reboot, my brightness is once again at maximum. Additionally, the
dim screen to save battery feature has actually been turning my brightness up. Then when I begin using my computer again after it dims the brightness is at max.